Does eating fat make you gain weight? Nutritionists answer

Carlos Sánchez 11 min. of reading Fats Leave a comment

There’s a lot of confusion around fat consumption and its link to weight gain. For decades, fats have been blamed as the main culprits behind overweight. But the real deal when it comes to gaining weight isn’t fat intake itself, it’s the total calorie surplus in your diet.

Eating more calories than your body needs, whether they come from fats, carbs, or proteins, leads to weight gain.

Answering the main question:

No, eating fat doesn’t automatically make you gain weight.
What really matters is the total energy balance: If you consume more calories than you burn, you’ll gain weight.

On the other hand, not all fats are created equal. Some fats are healthy and essential for the body, while others can be harmful when eaten in excess.

Among the functions of essential fats for good health, we find:

They promote the absorption of vitamins (A, D, E, and K).
They help hormone production.
They support brain and heart health.

FOODS	CALORIES per 100g
Avocado	160 kcal
Extra virgin olive oil	884 kcal
Walnuts	654 kcal
Almonds	579 kcal
Chia seeds	486 kcal
Flax seeds	534 kcal
Fatty fish (salmon)	208 kcal
Almond butter	614 kcal
Dark chocolate (85% or more)	598 kcal
Olives	115 kcal
Cashews	553 kcal
Pistachios	562 kcal

Table with main healthy fat foods and their calorie content

Don’t fear fats! In this article, we explain why you should stop being afraid of them and highlight which ones you should prioritize since they also help maintain overall good health.

Index

1 Types of fats
2 Myths and truths about fats and weight gain
3 What does the World Health Organization (WHO) say about fats?
4 Tips for healthy fat consumption

Types of fats

Fats are essential macronutrients for the body, but not all have the same impact on health. Here’s the difference between the main types of fats:

Fat Type	Characteristics	Main Sources	Health Effects
Saturated	Solid at room temperature.	Animal products: Butter, cheese, fatty meat. Tropical oils: Coconut, palm.	In excess, can raise LDL (“bad”) cholesterol. Linked to higher risk of cardiovascular diseases if consumed too much.
Unsaturated	Liquid at room temperature.	Monounsaturated: Olive oil, avocados, nuts. Polyunsaturated: Fatty fish, seeds, vegetable oils (sunflower, corn).	Heart-healthy and anti-inflammatory. Lower LDL cholesterol and raise HDL (“good”) cholesterol.
Trans	Chemically modified unsaturated fats (partial hydrogenation).	Ultra-processed products: Margarines, industrial pastries, fried foods.	Significantly raise LDL and lower HDL. Highly harmful: linked to higher risk of cardiovascular diseases and type 2 diabetes.

Saturated fats

For decades, saturated fats have been seen as one of the main factors responsible for raising cholesterol and increasing cardiovascular disease risk. However, more recent research has challenged this simplistic view and sparked debate about their real role in health.

Cardiovascular diseases are caused by a combination of factors, like chronic inflammation, oxidative stress, insulin resistance, and an overall unhealthy diet.
Instead of focusing only on saturated fats, it’s crucial to look at the overall diet and lifestyle context.

Several meta-analyses have found no significant link between saturated fat intake and increased heart disease risk in the general population.

However, some studies suggest replacing saturated fats with unsaturated fats can improve certain cardiovascular health markers.

Not all saturated fats are the same: Those from minimally processed foods (like good-quality meat and full-fat dairy) may not be as harmful as saturated fats found in ultra-processed foods.

For example, foods like coconut and dark chocolate contain saturated fats but also offer health benefits.

Unsaturated fats

Unsaturated fats are known as the “healthy fats” because of their many health benefits. These fats are liquid at room temperature and are divided into two main subtypes: monounsaturated and polyunsaturated, both essential for the body’s proper function.

Fats	Health Benefits	Main Sources
Monounsaturated	Help reduce LDL cholesterol and increase HDL. Support heart health by reducing inflammation and oxidative stress. Promote brain health, supporting cognitive function and protecting against neurodegenerative diseases.	Extra virgin olive oil. Avocados and guacamole. Almonds, hazelnuts, and cashews. Olives.
Polyunsaturated	Anti-inflammatory properties. Support brain development and function, especially during pregnancy and childhood. Promote cardiovascular health by lowering blood triglycerides and blood pressure. Support skin health, keeping it hydrated and flexible. Improve visual health and brain development.	Fatty fish (salmon, tuna, sardines). Flax and chia seeds. Walnuts and sunflower seeds. Fish oil and cod liver oil.

Trans fats

Trans fats are a type of fat artificially created through a chemical process called partial hydrogenation, where hydrogen is added to liquid vegetable oils to make them solid and more stable. While small amounts of natural trans fats are found in animal products like meat and dairy, most trans fats in the diet come from processed foods.

Health risks include:

Trans fats significantly raise LDL levels in the blood, contributing to plaque buildup in arteries and increasing atherosclerosis risk.
Besides raising bad cholesterol, trans fats lower good cholesterol, which protects the heart by removing excess cholesterol from arteries.
Due to their impact on cholesterol and ability to promote inflammation, trans fats are strongly linked to heart attacks, strokes, and other heart diseases.
They can worsen conditions like type 2 diabetes and obesity.
Also associated with higher risk of neurodegenerative diseases due to their effect on inflammation and oxidative stress.

Common sources of trans fats include: hydrogenated margarines and vegetable shortenings; industrial pastries like donuts, cookies, cakes, and pies; fried fast food (fries, fried chicken, breaded foods); ultra-processed foods listing partially hydrogenated fats in their ingredients.

Myths and truths about fats and weight gain

For years, fats have been unfairly demonized as the main cause of weight gain. However, modern research shows the picture is way more complex.

The myth that “fats alone make you fat” is outdated.

Science supports a more nuanced view: It’s calorie surplus and inactivity, not fats themselves, that are the real culprits behind weight gain.

Myth: All fats make you gain weight equally.

Reality: Not all fats affect the body the same way or contribute to weight gain equally.

Healthy fats (monounsaturated and polyunsaturated) are essential for body function and can even help maintain a healthy weight by promoting satiety and metabolism. Trans fats and excessive saturated fat intake, especially in the context of an unbalanced diet, can have negative effects.

Myth: Eating fat automatically turns into body fat.

Reality: Weight gain depends on total calorie surplus, not just fat intake. If you consume more calories than your body burns, whether from fats, carbs, or proteins, those extra calories will be stored as body fat.

Myth: A low-fat diet is the best way to lose weight.

Reality: Low-fat diets aren’t necessarily more effective than others. Fats provide satiety and are essential for vital functions like hormone production and absorption of fat-soluble vitamins (A, D, E, and K).

Cutting out or drastically reducing fats can lead to nutritional deficiencies and increased intake of refined carbs, which can promote weight gain.

Truth: Calorie surplus and physical inactivity are the main causes of weight gain.

Calorie surplus: Eating more calories than your body needs, regardless of whether they come from fats, carbs, or proteins, leads to body fat storage.

Inactivity lowers daily calorie expenditure, making it easier to have a positive energy balance (intake greater than expenditure) and thus gain weight.

What does the World Health Organization (WHO) say about fats?

The World Health Organization (WHO) provides clear guidelines on fat consumption and its relation to health. These recommendations aim to reduce the risk of cardiovascular diseases, obesity, and other diet-related health issues.

1. Total fat intake:

Fats should make up between 20% and 35% of total daily calorie intake in a balanced diet.
The specific amount depends on individual needs like age, physical activity level, and health conditions.

2. Saturated fats:

Saturated fat intake should be limited to less than 10% of total daily calories.
WHO recommends replacing saturated fats with unsaturated fats whenever possible to improve cardiovascular health.

3. Trans fats:

Trans fat intake should be kept below 1% of total daily calories.
Ideally, they should be completely eliminated from the diet, as they offer no health benefits and are strongly linked to cardiovascular diseases.

4. Unsaturated fats:

Both monounsaturated and polyunsaturated fats should be the main fat sources in the diet.
Recommended sources: olive oil, avocados, fatty fish, nuts, and seeds.

5. Focus on fat quality:

WHO emphasizes prioritizing natural and minimally processed foods to get healthy fats.
It recommends avoiding ultra-processed foods containing trans fats and high amounts of saturated fats, like fast food, industrial pastries, and fried foods.

Tips for healthy fat consumption

Including healthy fats in your daily diet is key for your body’s proper function. But it’s important to do it in balance to avoid calorie overload. Here are practical tips to enjoy the benefits of healthy fats without compromising your health or weight:

1. Prioritize unsaturated fat sources

Use olive oil as a dressing for salads or for low-heat cooking.
Add avocado slices to toast, salads, or smoothies.
Snack on a handful (30 g) of walnuts, almonds, chia, or flax seeds, or add them to yogurts and cereals.
Include fish like salmon, tuna, or sardines twice a week.

2. Watch your portions

Even though healthy fats are beneficial, they’re calorie-dense. Examples of appropriate portions:

1 tablespoon of olive oil (120 kcal).
¼ avocado (60–80 kcal).
1 handful of nuts (30 g, about 200 kcal).

3. Swap less healthy fats

Replace butter with olive oil or avocado on toast or in recipes.
Choose lean cuts of meat instead of fatty ones.
Avoid trans fats: Check processed food labels and avoid those with partially hydrogenated fats.

4. Add healthy fats to main meals

Drizzle a bit of olive oil on pasta, rice, or veggies.
Use avocado or hummus as a healthy alternative to mayo or creamy dressings.
Sprinkle flax, sesame, or chia seeds on salads, soups, or smoothies.

5. Cook healthily

Use cooking methods like roasting, baking, steaming, or sautéing instead of frying.
Limit the amount of oil used by spraying or measuring with a teaspoon.

6. Plan healthy snacks

Swap ultra-processed snacks for natural options like yogurt with chia seeds or apple slices with almond butter and chocolate crums.

7. Balance your meals

Combine healthy fats with complex carbs (like whole grain bread, rice, or quinoa) and lean proteins (like chicken, fish, or legumes) for a complete, nutritious meal.

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